Planetary gear train of automatic transmission for vehicle

ABSTRACT

A planetary gear train of an automatic transmission for a vehicle may include an input shaft configured for receiving an engine torque, an output shaft configured for outputting a shifted torque of the engine, a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, six control elements for selectively interconnecting rotation elements of the planetary gear sets and a transmission housing, a first connecting member selectively connected to the transmission housing, a second connecting member selectively connected to the transmission housing, a third connecting member directly connected to the input shaft, a fourth connecting member selectively connected to the transmission housing, a fifth connecting member selectively connected to the input shaft, and selectively connected to the transmission housing, a sixth connecting member directly connected to the output shaft, and a seventh connecting member selectively connected to the input shaft.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2015-0170975, filed Dec. 2, 2015, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic transmission for a vehicle.

Description of Related Art

Recent increases in oil prices are triggering hard competition among auto-makers in enhancing fuel consumption of a vehicle.

In this sense, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted to ensure both drivability and competitiveness for maximizing fuel efficiency by implementing an automatic transmission with multiple speed stages.

However, in the case of the automatic transmission, the number of internal components increases as the number of gear shift stages is increased, which may deteriorate installability, production cost, weight and/or power flow efficiency.

Therefore, in order to maximally enhance fuel consumption of an automatic transmission having increased shift stages, it is important for improved efficiency to be derived by a smaller number of parts.

In this respect, an eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission enabling more shift stages is under investigation.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for a vehicle having advantages of, by minimal complexity, realizing at least nine forward speeds and at least one reverse speed, increasing a gear ratio span so as to improve power delivery performance and fuel consumption, and achieving driving stability of a vehicle by utilizing a low rotation speed of an engine.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque of the engine, a first planetary gear set including first, second, and third rotation elements, a second planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set including seventh, eighth, and ninth rotation elements, a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements, six control elements for selectively interconnecting the rotation elements and a transmission housing, a first connecting member connected to the first rotation element and selectively connected to the transmission housing, a second connecting member connected to the second rotation element, sixth rotation element, seventh rotation element and selectively connected to the transmission housing, a third connecting member connected to the third rotation element and the fourth rotation element, and directly connected to the input shaft, a fourth connecting member connected to the fifth rotation element, and selectively connected to the transmission housing, a fifth connecting member connected to the eighth rotation element and the twelfth rotation element, selectively connected to the input shaft, and selectively connected to the transmission housing, a sixth connecting member connected to the ninth rotation element and the eleventh rotation element and directly connected to the output shaft, and a seventh connecting member connected to the tenth rotation element, and selectively connected to the input shaft.

The first planetary gear set may be a single pinion planetary gear set, where the first rotation element may be a first sun gear, the second rotation element may be a first planet carrier, and the third rotation element may be a first ring gear, the second planetary gear set may be a single pinion planetary gear set, where the fourth rotation element may be a second sun gear, the fifth rotation element may be a second planet carrier, and the sixth rotation element may be a second ring gear, the third planetary gear set may be a single pinion planetary gear set, where the seventh rotation element may be a third sun gear, the eighth rotation element may be a third planet carrier, and the ninth rotation element may be a third ring gear, and the fourth planetary gear set may be a single pinion planetary gear set, where the tenth rotation element may be a fourth sun gear, the eleventh rotation element may be a fourth planet carrier, and the twelfth rotation element may be a fourth ring gear.

The six control elements may include a first clutch selectively connecting the input shaft and the fifth connecting member, a second clutch selectively connecting the input shaft and the seventh connecting member, a first brake selectively connecting the first connecting member and the transmission housing, a second brake selectively connecting the second connecting member and the transmission housing, a third brake selectively connecting the fourth connecting member and the transmission housing, and a fourth brake selectively connecting the fifth connecting member and the transmission housing.

Shift stages realized by selective operation of the six control elements may include a forward first speed formed by simultaneous operation of the third and fourth brakes, a forward second speed formed by simultaneous operation of the second clutch and the fourth brake, a forward third speed formed by simultaneous operation of the second clutch and the third brake, a forward fourth speed formed by simultaneous operation of the second clutch and the second brake, a forward fifth speed formed by simultaneous operation of the second clutch and the first brake, a forward sixth speed formed by simultaneous operation of the first and second clutches, a forward seventh speed formed by simultaneous operation of the first clutch and the first brake, a forward eighth speed formed by simultaneous operation of the first clutch and the second brake, a forward ninth speed formed by simultaneous operation of the first clutch and the third brake, and a reverse speed formed by simultaneous operation of the first and fourth brakes.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque of the engine, a first planetary gear set as a single pinion planetary gear set including first, second, and third rotation elements, a second planetary gear set as a single pinion planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set as a single pinion planetary gear set including seventh, eighth, and ninth rotation elements, a fourth planetary gear set as a single pinion planetary gear set including tenth, eleventh, and twelfth rotation elements, a first connecting member connected to the first rotation element and selectively connected to the transmission housing, a second connecting member connected to the second rotation element, sixth rotation element, seventh rotation element and selectively connected to the transmission housing, a third connecting member connected to the third rotation element and the fourth rotation element, and directly connected to the input shaft, a fourth connecting member connected to the fifth rotation element, and selectively connected to the transmission housing, a fifth connecting member connected to the eighth rotation element and the twelfth rotation element, selectively connected to the input shaft, and selectively connected to the transmission housing, a sixth connecting member connected to the ninth rotation element and the eleventh rotation element and directly connected to the output shaft, a seventh connecting member connected to the tenth rotation element, and selectively connected to the input shaft, a first clutch selectively connecting the input shaft and the fifth connecting member, a second clutch selectively connecting the input shaft and the seventh connecting member, a first brake selectively connecting the first connecting member and the transmission housing, a second brake selectively connecting the second connecting member and the transmission housing, a third brake selectively connecting the fourth connecting member and the transmission housing, and a fourth brake selectively connecting the fifth connecting member and the transmission housing.

The first planetary gear set may include a first sun gear as the first rotation element, a first planet carrier as the second rotation element, and a first ring gear as the third rotation element, the second planetary gear set may include a second sun gear as the fourth rotation element, a second planet carrier as the fifth rotation element, and a second ring gear as the sixth rotation element, the third planetary gear set may include a third sun gear as the seventh rotation element, a third planet carrier as the eighth rotation element, and a third ring gear as the ninth rotation element, and the fourth planetary gear set may include a fourth sun gear as the tenth rotation element, a fourth planet carrier as the eleventh rotation element, and a fourth ring gear as the twelfth rotation element.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque of the engine, a first planetary gear set as a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear, a second planetary gear set as a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear, a third planetary gear set as a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear, a fourth planetary gear set as a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear, a first connecting member connected to the first sun gear and selectively connected to the transmission housing, a second connecting member connected to the second planet carrier, second ring gear, third sun gear and selectively connected to the transmission housing, a third connecting member connected to the first ring gear and the second sun gear, and directly connected to the input shaft, a fourth connecting member connected to the second planet carrier, and selectively connected to the transmission housing, a fifth connecting member connected to the third planet carrier and the fourth ring gear, selectively connected to the input shaft, and selectively connected to the transmission housing, a sixth connecting member connected to the third ring gear and the fourth planet carrier, and directly connected to the output shaft, a seventh connecting member connected to the fourth sun gear, and selectively connected to the input shaft, and six control elements selectively connecting the connecting members and the transmission housing.

A planetary gear train according to various embodiment of the present invention may realize at least nine forward speeds and at least one reverse speed, achieved by operating the four planetary gear sets as simple planetary gear sets by controlling six control elements.

In addition, a planetary gear train according to various embodiments of the present invention substantially improves driving stability by realizing shift stages appropriate for rotation speed of an engine due to multiple speed stages of an automatic transmission.

In addition, a planetary gear train according to various embodiments of the present invention may maximize engine driving efficiency by multiple speed-stages of an automatic transmission, and may improve power delivery performance and fuel consumption.

It is understood that the term “vehicle” or “vehicular” or other similar terms as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary planetary gear train according to the present invention.

FIG. 2 is an operational chart for respective control elements at respective shift stages in the exemplary planetary gear train according to the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of a planetary gear train according to various embodiments of the present invention. Referring to FIG. 1, a planetary gear train according to various embodiments of the present invention includes first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4 arranged on a same axis, an input shaft IS, an output shaft OS, seven connecting members TM1 to TM7 for interconnecting rotation elements of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, six control elements C1 to C2 and B1 to B4, and a transmission housing H.

Torque input from the input shaft IS is shifted by cooperative operation of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, and then output through the output shaft OS.

The simple planetary gear sets are arranged in the order of first, first, second, third and fourth planetary gear sets PG1, PG2, PG3 and PG4, from an engine side.

The input shaft IS is an input member and the torque from a crankshaft of an engine, after being torque-converted through a torque converter, is input into the input shaft IS.

The output shaft OS is an output member, and being arranged on a same axis with the input shaft IS, delivers a shifted torque to a drive shaft through a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear set, and includes a first sun gear S1, a first planet carrier PC1 that supports a first pinion P1 externally engaged with the first sun gear S1, and a first ring gear R1 internally engaged with the first pinion P1. The first sun gear S1 acts as a first rotation element N1, the first planet carrier PC1 acts as a second rotation element N2, and the first ring gear R1 acts as a third rotation element N3.

The second planetary gear set PG2 is a single pinion planetary gear set, and includes a second sun gear S2, a second planet carrier PC2 that supports a second pinion P2 externally engaged with the second sun gear S2, and a second ring gear R2 internally engaged with the second pinion P2. The second sun gear S2 acts as a fourth rotation element N4, the second planet carrier PC2 acts as a fifth rotation element N5, and the second ring gear R2 acts as a sixth rotation element N6.

The third planetary gear set PG3 is a single pinion planetary gear set, and includes a third sun gear S3, a third planet carrier PC3 that supports a third pinion P3 externally engaged with the third sun gear S3, and a third ring gear R3 internally engaged with the third pinion P3. The third sun gear S3 acts as a seventh rotation element N7, the third planet carrier PC3 acts as an eighth rotation element N8, and the third ring gear R3 acts as a ninth rotation element N9.

The fourth planetary gear set PG4 is a single pinion planetary gear set, and includes a fourth sun gear S4, a fourth planet carrier PC4 that supports a fourth pinion P4 externally engaged with the fourth sun gear S4, and a fourth ring gear R4 internally engaged with the fourth pinion P4. The fourth sun gear S4 acts as a tenth rotation element N10, the fourth planet carrier PC4 acts as an eleventh rotation element N11, and the fourth ring gear R4 acts as a twelfth rotation element N12.

In the arrangement of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, the second rotation element N2 is directly connected with the sixth rotation element N6 and the seventh rotation element N7, the third rotation element N3 is directly connected with the fourth rotation element N4, the eighth rotation element N8 is directly connected with the twelfth rotation element N12, and the ninth rotation element N9 is directly connected with the eleventh rotation element N11, by seven connecting members TM1 to TM7.

The seven connecting members TM1 to TM7 are arranged as follows.

The first connecting member TM1 is connected with the first rotation element N1 (first sun gear S1), and selectively connected with the transmission housing H, thereby acting as a selective fixed element.

The second connecting member TM2 is connected with the second rotation element N2 (first planet carrier PC1) and sixth rotation element N6 (second ring gear R2) and the seventh rotation element N7 (third sun gear S3), and selectively connected with the transmission housing H, thereby acting as a selective fixed element.

The third connecting member TM3 is connected with the third rotation element N3 (first ring gear R1) and the fourth rotation element N4 (second sun gear S2), and directly connected with the input shaft IS, thereby always acting as an input element.

The fourth connecting member TM4 is connected with the fifth rotation element N5 (second planet carrier PC2), and selectively connected with the transmission housing H, thereby acting as a selective fixed element.

The fifth connecting member TM5 is connected with the eighth rotation element N8 (third planet carrier PC3) and the twelfth rotation element N12 (fourth ring gear R4), selectively connected with the input shaft IS thereby acting as a selective input element, and selectively connected with the transmission housing H thereby acting as a selective fixed element.

The sixth connecting member TM6 is connected with the ninth rotation element N9 (third ring gear R3) and eleventh rotation element N11 (fourth planet carrier PC4), and directly connected with the output shaft OS, thereby always acting as an output element.

The seventh connecting member TM7 is connected with the tenth rotation element N10 (fourth sun gear S4), and selectively connected with the input shaft IS, thereby acting as a selective input element.

The connecting members TM1 to TM7 may be selectively interconnected with one another by control elements of two clutches C1 and C2.

The connecting members TM1 to TM7 may be selectively connected with the transmission housing H, by control elements of four brakes B1, B2, B3, and B4.

The six control elements C1 to C2 and B1 to B4 are arranged as follows.

The first clutch C1 is arranged between the input shaft IS and the fifth connecting member TM5, such that the input shaft IS and the fifth connecting member TM5 may selectively become integral.

The second clutch C2 is arranged between the input shaft IS and the seventh connecting member TM7, such that the input shaft IS and the seventh connecting member TM7 may selectively become integral.

The first brake B1 is arranged between the first connecting member TM1 and the transmission housing H, such that the first connecting member TM1 may selectively act as a fixed element.

The second brake B2 is arranged between the second connecting member TM2 and the transmission housing H, such that the second connecting member TM2 may selectively act as a fixed element.

The third brake B3 is arranged between the fourth connecting member TM4 and the transmission housing H, such that the fourth connecting member TM4 may selectively act as a fixed element.

The fourth brake B4 is arranged between the fifth connecting member TM5 and the transmission housing H, such that the fifth connecting member TM5 may selectively act as a fixed element.

The control elements of the first and second clutches C1 and C2 and the first, second, third, and fourth brakes B1, B2, B3, and B4 may be realized as multi-plate hydraulic pressure friction devices that are frictionally engaged by hydraulic pressure.

FIG. 2 is an operational chart for respective control elements at respective shift stages in a planetary gear train according to various embodiments of the present invention. As shown in FIG. 2, a planetary gear train according to various embodiments of the present invention performs shifting by operating two control elements at respective shift stages.

In the forward first speed shift stage D1, the third and fourth brakes B3 and B4 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3, and the fourth connecting member TM4 and the fifth connecting member TM5 simultaneously act as fixed elements by the operation of the third and fourth brakes B3 and B4, thereby realizing the forward first speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward second speed shift stage D2, the second clutch C2 and the fourth brake B4 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the seventh connecting member TM7 by the operation of the second clutch C2. In addition, the fifth connecting member TM5 acts as a fixed element by the operation of the fourth brake B4, thereby realizing the forward second speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward third speed shift stage D3, the second clutch C2 and the third brake B3 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the seventh connecting member TM7 by the operation of the second clutch C2. In addition, the fourth connecting member TM4 acts as a fixed element by the operation of the third brake B3, thereby realizing the forward third speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward fourth speed shift stage D4, the second clutch C2 and the second brake B2 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the seventh connecting member TM7 by the operation of the second clutch C2. In addition, the second connecting member TM2 acts as a fixed element by the operation of the second brake B2, thereby realizing the forward fourth speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward fifth speed shift stage D5, the second clutch C2 and the first brake B1 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the seventh connecting member TM7 by the operation of the second clutch C2. In addition, the first connecting member TM1 acts as a fixed element by the operation of the first brake B1, thereby realizing the forward fifth speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward sixth speed shift stage D6, the first and second brakes C1 and C2 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the fifth, seventh connecting member (TM5, TM7) by the operation of the first and second clutches C1 and C2. Then, the fourth planetary gear set PG4 becomes integral, and realizes the forward sixth speed, outputting an inputted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward seventh speed shift stage D7, the first clutch C1 and the second brake B2 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the fifth connecting member TM5 by the operation of the first clutch C1. In addition, the first connecting member TM1 acts as a fixed element by the operation of the first brake B1, thereby realizing the forward seventh speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward eighth speed shift stage D8, the first clutch C1 and the second brake B2 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the fifth connecting member TM5 by the operation of the first clutch C1. In addition, the second connecting member TM2 acts as a fixed element by the operation of the second brake B2, thereby realizing the forward eighth speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the forward ninth speed shift stage D9, the first clutch C1 and the third brake B3 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3 and simultaneously to the fifth connecting member TM5 by the operation of the first clutch C1. In addition, the fourth connecting member TM4 acts as a fixed element by the operation of the third brake B3, thereby realizing the forward ninth speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

In the reverse speed REV, the first and fourth brakes B1 and B4 are simultaneously operated. As a result, torque of the input shaft IS is input to the third connecting member TM3, and the first connecting member TM1 and the fifth connecting member TM5 simultaneously act as fixed elements by the operation of the first and fourth brakes B1 and B4, thereby realizing the reverse speed and outputting a shifted torque through the output shaft OS connected with the sixth connecting member TM6.

As described above, a planetary gear train according to various embodiments of the present invention may realize forward nine speeds and one reverse speed formed by operating the four planetary gear sets PG1, PG2, PG3, and PG4 by controlling the two clutches C1 and C2 and the four brakes B1, B2, B3, and B4.

In addition, a planetary gear train according to various embodiments of the present invention may substantially improve driving stability by realizing shift stages appropriate for rotation speed of an engine due to multi-stages of an automatic transmission.

In addition, a planetary gear train according to various embodiments of the present invention may maximize engine driving efficiency by multi-stages of an automatic transmission, and may improve power delivery performance and fuel consumption.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft configured for receiving an engine torque; an output shaft configured for outputting a shifted torque of the engine; a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements; six control elements each of which selectively interconnects a corresponding pair among the input shaft, the output shaft, the first to twelfth rotation elements and a transmission housing; a first connecting member fixedly connected to the first rotation element and selectively connected to the transmission housing; a second connecting member fixedly connected to the second rotation element, the sixth rotation element, and the seventh rotation element such that the second, sixth, and seventh rotation elements always rotate at a same speed and selectively connected to the transmission housing; a third connecting member connected to the third rotation element and the fourth rotation element such that the third and fourth rotation elements always rotate at a same speed, and fixedly connected to the input shaft; a fourth connecting member connected to the fifth rotation element, and selectively connected to the transmission housing; a fifth connecting member connected to the eighth rotation element and the twelfth rotation element such that the eighth and twelfth rotation elements always rotate at a same speed, selectively connected to the input shaft, and selectively connected to the transmission housing; a sixth connecting member connected to both of the ninth rotation element and the eleventh rotation element such that the ninth and eleventh rotation elements always rotate at a same speed, and directly connected to the output shaft; and a seventh connecting member connected to the tenth rotation element, and selectively connected to the input shaft.
 2. The planetary gear train of claim 1, wherein the first planetary gear set is a single pinion planetary gear set, where the first rotation element is a first sun gear, the second rotation element is a first planet carrier, and the third rotation element is a first ring gear; the second planetary gear set is a single pinion planetary gear set, where the fourth rotation element is a second sun gear, the fifth rotation element is a second planet carrier, and the sixth rotation element is a second ring gear; the third planetary gear set is a single pinion planetary gear set, where the seventh rotation element is a third sun gear, the eighth rotation element is a third planet carrier, and the ninth rotation element is a third ring gear; and the fourth planetary gear set is a single pinion planetary gear set, where the tenth rotation element is a fourth sun gear, the eleventh rotation element is a fourth planet carrier, and the twelfth rotation element is a fourth ring gear.
 3. The planetary gear train of claim 1, wherein the six control elements comprise: a first clutch selectively connecting the input shaft and the fifth connecting member; a second clutch selectively connecting the input shaft and the seventh connecting member; a first brake selectively connecting the first connecting member and the transmission housing; a second brake selectively connecting the second connecting member and the transmission housing; a third brake selectively connecting the fourth connecting member and the transmission housing; and a fourth brake selectively connecting the fifth connecting member and the transmission housing.
 4. The planetary gear train of claim 3, wherein shift stages realized by selective operation of the six control elements comprise: a forward first speed formed by operation of the third and fourth brakes; a forward second speed formed by operation of the second clutch and the fourth brake; a forward third speed formed by operation of the second clutch and the third brake; a forward fourth speed formed by operation of the second clutch and the second brake; a forward fifth speed formed by operation of the second clutch and the first brake; a forward sixth speed formed by operation of the first and second clutches; a forward seventh speed formed by operation of the first clutch and the first brake; a forward eighth speed formed by operation of the first clutch and the second brake; a forward ninth speed formed by operation of the first clutch and the third brake; and a reverse speed formed by operation of the first and fourth brakes.
 5. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft configured for receiving an engine torque; an output shaft configured for outputting a shifted torque of the engine; a first planetary gear set as a single pinion planetary gear set including first, second, and third rotation elements; a second planetary gear set as a single pinion planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set as a single pinion planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set as a single pinion planetary gear set including tenth, eleventh, and twelfth rotation elements; a first connecting member fixedly connected to the first rotation element and selectively connected to a transmission housing; a second connecting member fixedly connected to the second rotation element, the sixth rotation element, and the seventh rotation element such that the second, sixth, and seventh rotation elements always rotate at a same speed, and selectively connected to the transmission housing; a third connecting member fixedly connected to the third rotation element and the fourth rotation element such that the third and fourth rotation elements always rotate at a same speed, and fixedly connected to the input shaft; a fourth connecting member fixedly connected to the fifth rotation element, and selectively connected to the transmission housing; a fifth connecting member fixedly connected to the eighth rotation element and the twelfth rotation element such that the eighth and twelfth rotation elements always rotate at a same speed, selectively connected to the input shaft, and selectively connected to the transmission housing; a sixth connecting member fixedly connected to both of the ninth rotation element and the eleventh rotation element such that the ninth and eleventh rotation elements always rotate at a same speed, and directly connected to the output shaft; a seventh connecting member fixedly connected to the tenth rotation element, and selectively connected to the input shaft; a first clutch selectively connecting the input shaft and the fifth connecting member; a second clutch selectively connecting the input shaft and the seventh connecting member; a first brake selectively connecting the first connecting member and the transmission housing; a second brake selectively connecting the second connecting member and the transmission housing; a third brake selectively connecting the fourth connecting member and the transmission housing; and a fourth brake selectively connecting the fifth connecting member and the transmission housing.
 6. The planetary gear train of claim 5, wherein the first planetary gear set includes a first sun gear as the first rotation element, a first planet carrier as the second rotation element, and a first ring gear as the third rotation element; the second planetary gear set includes a second sun gear as the fourth rotation element, a second planet carrier as the fifth rotation element, and a second ring gear as the sixth rotation element; the third planetary gear set includes a third sun gear as the seventh rotation element, a third planet carrier as the eighth rotation element, and a third ring gear as the ninth rotation element; and the fourth planetary gear set includes a fourth sun gear as the tenth rotation element, a fourth planet carrier as the eleventh rotation element, and a fourth ring gear as the twelfth rotation element.
 7. The planetary gear train of claim 5, wherein shift stages realized by selective operation of the two clutch and the four brakes comprise: a forward first speed formed by operation of the third and fourth brakes; a forward second speed formed by operation of the second clutch and the fourth brake; a forward third speed formed by operation of the second clutch and the third brake; a forward fourth speed formed by operation of the second clutch and the second brake; a forward fifth speed formed by operation of the second clutch and the first brake; a forward sixth speed formed by operation of the first and second clutches; a forward seventh speed formed by operation of the first clutch and the first brake; a forward eighth speed formed by operation of the first clutch and the second brake; a forward ninth speed formed by operation of the first clutch and the third brake; and a reverse speed formed by operation of the first and fourth brakes.
 8. A planetary gear train of an automatic transmission for a vehicle, comprising: an input shaft configured for receiving an engine torque; an output shaft configured for outputting a shifted torque of the engine; a first planetary gear set as a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear; a second planetary gear set as a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear; a third planetary gear set as a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear; a fourth planetary gear set as a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear; a first connecting member fixedly connected to the first sun gear and selectively connected to a transmission housing; a second connecting member fixedly connected to the first planet carrier, the second ring gear, and the third sun gear such that the first planet carrier, the second ring gear, and the third sun gear always rotate at a same speed, and selectively connected to the transmission housing; a third connecting member fixedly connected to the first ring gear and the second sun gear such that the first ring gear and the second sun gear always rotate at a same speed, and fixedly connected to the input shaft; a fourth connecting member fixedly connected to the second planet carrier, and selectively connected to the transmission housing; a fifth connecting member fixedly connected to the third planet carrier and the fourth ring gear such that the third planet carrier and the fourth ring gear always rotate at a same speed, selectively connected to the input shaft, and selectively connected to the transmission housing; a sixth connecting member fixedly connected to both of the third ring gear and the fourth planet carrier such that the third ring gear and the fourth planet carrier always rotate at a same speed, and fixedly connected to the output shaft; a seventh connecting member fixedly connected to the fourth sun gear, and selectively connected to the input shaft; and six control elements each of which selectively connects a corresponding pair among the input shaft, the output shaft, the first to seventh connecting members and the transmission housing.
 9. The planetary gear train of claim 8, wherein the six control elements comprise: a first clutch selectively connecting the input shaft and the fifth connecting member; a second clutch selectively connecting the input shaft and the seventh connecting member; a first brake selectively connecting the first connecting member and the transmission housing; a second brake selectively connecting the second connecting member and the transmission housing; a third brake selectively connecting the fourth connecting member and the transmission housing; and a fourth brake selectively connecting the fifth connecting member and the transmission housing.
 10. The planetary gear train of claim 9, wherein shift stages realized by selective operation of the six control elements comprise: a forward first speed formed by operation of the third and fourth brakes; a forward second speed formed by operation of the second clutch and the fourth brake; a forward third speed formed by operation of the second clutch and the third brake; a forward fourth speed formed by operation of the second clutch and the second brake; a forward fifth speed formed by operation of the second clutch and the first brake; a forward sixth speed formed by operation of the first and second clutches; a forward seventh speed formed by operation of the first clutch and the first brake; a forward eighth speed formed by operation of the first clutch and the second brake; a forward ninth speed formed by operation of the first clutch and the third brake; and a reverse speed formed by operation of the first and fourth brakes. 